Dehydrohalogenation of quaternary carbon atom-containing halogenated hydrocarbons



United States Patent 3,415,897 DEHYDROHALOGENATION 0F QUATERNARY CARBONATOM-CONTAINING HALOGENATED HYDROCARBONS Gary L. Gehrman, Homewood, andByron W. Turnquest, Chicago, Ill., assignors to Sinclair Research Inc.,New York, N.Y., a corporation of Delaware No Drawing. Filed Aug. 3,1966, Ser. No. 569,811 Claims. (Cl. 260-677) ABSTRACT OFTHE DISCLOSUREQuaternary carbon atom-containing halogenated hydrocarbons of theformula:

wherein R is an alkyl radical of up to 8 carbon atoms, the total carbonatoms in the three R groups being up to 18, R is a divalent hydrocarbonradical of 2 to 8 carbon atoms, and X is a halogen having an atomicweight of 35 to 127 (e.g. neohexyl chloride) are thermallydehydrohalogenated to the corresponding mono-olefins by first forming anintermediate complex of the halogenated hydrocarbon with collidine,followed by decomposing the intermediate complex to yield thecorresponding quaternary carbon atom-containing mono-olefin. At leastequimolar amounts of collidine are used, based on the amount ofhalogenated hydrocarbon feed.

The present invention relates to the production of substantially purequaternary carbon atom-containing monoolefins by the dehydrohalogenationof quaternary carbon atom-containing halogenated hydrocarbons.

' Heretofore, methods for the production of quaternary carbonatom'containing olefins such as neohexene (3,3-dimethylbutene-l) bythermal dehydrohalogenation of the corresponding halogenatedhydrocarbon, provide a reaction product that includes, in addition tothe quaternary carbon atom-containing mono-olefin, certain side reactionproducts and hydrogen halide which can be removed by any of the knownprocedures of the art as, for instance, by fractional distillation.However, since side products formed in the dehydrohalogenation aretertiary olefins having boiling points close to that of the desiredquaternary carbon atom-containing mono-olefin, removal of these sideproducts by straight fractionation is difficult and requires highefficiency and costly fractionation equipment.

A process for the dehydrohalogenation of quaternary carbon-containingalkyl halides to the corresponding quaternary carbon-containingmonoolefins has now been discovered which not only provides the desiredproduct in essentially pure form but in yields of at least 85 molepercent and even greater than 90 mole percent. In accordanee with thepresent invention, a quaternary carboncontaining alkyl halide feed isthermally dehydrohalogenated in the presence of collidine, in aparticular manner, employing two different ranges of reactiontemperatures. We have found that the neoalkyl halide feed of theinvention reacts with collidine under select temperatures, i.e., about300 to 370 F. to form an intermediate complex with collidine, and thatthe intermediate complex com pletely decomposes when subjected to a heattreatment at elevated temperatures below the decomposition temperatureof collidine, usually at least 440 F. up to 500 F., to provide thedesired quaternary carbon-containing monoolefin and collidinehydrohalide, At least a molar equiv- Patented Dec. 10, 1968 alent,preferably a molar excess, of collidine is reacted with the neoalkylhalide feed. In general, a mole ratio of collidine to neoalkyl halidefeed of about 1 to 20, preferably about 1 to 5 moles of collidine permole of neoalkyl halide is employed at a temperature of about 300 to 370F. for a time sufficient to form the intermediate complex, and theintermediate complex is subjected to heat treatment at a temperature ofabout 440 to 500 F. while recovering the corresponding quaternarycarbon-containingmono-olefin and collidine hydrohalide. The reactiontime of the neoalkyl halide feed and collidine will vary according tothe particular temperature selected but is that sufficient to form theintermediate complex. In most instances, the reaction time is at leastabout 2 hours, preferably at least about 5 hours. Normally, heating thereactants from ambient temperature to 400 F. in a batch system givessuflicient time to form the intermediate in the low temperature phase.In a flow system, however, where the reactor is held at approximately400 F., little or no intermediate formation or dehydrohalogenation takesplace unless a low temperature zone has been included.

The reaction temperatures employed in the dehydrohalogenation process ofthe invention are extremely important in obtaining yields of the desiredproducts in excess of mole percent. For example, if the neoalkyl halidesfeed and the collidine are subjected initially to too high a temperature(i.e., beyond about 370 F.) the intermediate will not form. Likewise, ifthe high temperature second stage of the invention (i.e., beyond about440 F.) is not included, the intermediate complex formed in the firststage will not properly decompose into the desired product resulting inconsiderable yield loss. Moreover, complete decomposition of theintermediate is desired not only to obtain the high yield reaction butalso for the recovery of collidine. If the high temperature stage of theinvention is not included in the process, the collidine hydrohalideforms an agglomerate with the undecomposed intermediate and is recoveredas rather large spheres, approximately 2 to 5 mm. in diameter. When thehigh temperature second stage of the invention is employed in theprocess, the resulting collidine hydrohalide is, in contrast, in theform of minute crystalline needles. The resulting size and form of thecollidine hydrohalide product is of importance when recovering collidineby regeneration from its hydrohalide salt with anhydrous ammonia. Theminute crystalline needles from the high temperature reaction respondvery well to ammonia treatment whereas the spheres of collidinehydrohalide resulting from a reaction in which the second stage hightemperature treatment was not included do not react readily withanhydrous ammonia and collidine recovery is very difficult.

The halogenated hydrocarbon feed subjected to the dehydrohalogenation ofthe present invention may be rep resented by the general formula:

wherein R is an aliphatic monovalent hydrocarbon radical such as a loweralkyl, including cycloallkyl, of up to 8 carbons, the total carbon atomsin all Rs being up to 18, preferably up to 12, and R may be branched orsubstituted with noninterfering groups; R is a divalent aliphatichydrocarbon radical, e.g., alkylene, of 2 to 8 carbons, preferably 2 to4 carbon atoms; and X is a halogen atom having an atomic weight of 35 to127. Preferably, the halogen is substituted on a carbon atom beta to theneo-carbon atom. It is particularly preferred that the beta carbon atombe at an end of the carbon chain. Suitable feeds include, for instance,1-chloro-3,3-dimethylbutane; 1-chloro-3,3-dimethylpentane;2hloro-4,4-dimethylpentane, etc.

The following examples are included to further illustrate the process ofthe present invention:

EXAMPLE 1 8.4 moles of collidine and 7 moles of neohexyl chloride (1.2:1mole ratio) were charged to a one gallon glasslined stirred autoclave.The temperature was maintained at 330 F. After 8 hours low-boilingproducts were discharged overhead through a water-cooled condenser intoDry Ice traps. A 10 mole percent yield of neohexene was obtained.Reactor residue contained only collidine, neohexyl chloride and a smallamount of collidine hydrochloride.

EXAMPLE 2 12.8 moles of collidine and 10.7 moles of neohexyl chloride(1.2:1 mole ratio) were charged to the autoclave described in Example 1.Temperature was maintained at 350 F. After 7 hours low-boiling productswere discharged overhead through a water-cooled condenser into Dry Icetraps. 15 mole percent neohexene was obtained. The reactor residuecontained collidine, neohexyl chloride and an insoluble tar-likematerial mixed with the collidine hydrochloride.

EXAMPLE 3 The liquid phase was decanted from the reactor residue fromExample 2. The remaining solid phase was treated with acetone. The tarwas very soluble and crystals of collidine hydrochloride were removed byfiltration. The solvent and residual collidine and neohexyl chloridewere removed by vacuum distillation. The remaining tar was submitted forcarbon, hydrogen and chlorine analysis. The results of the analysislisted in Table I indicate that the I By difierence.

A sample of the intermediate was heated in a distillation apparatus atatmospheric pressure. It partially decomposed at 405 F. to yield 28 wt.percent neohexene, 15 wt. percent neohexyl-chloride, collidinehydrochloride and higher boiling material.

EXAMPLE 4 12.8 moles of collidine and 10.7 moles of neohexyl chloride(1.211 mole ratio) were charged to the autoclave described in Example 1.Temperature was maintained at 390405 F. Low-boiling products weredischarged overhead throughout the experiment at a rate sufficient tomaintain reactor pressure at 100 p.s.i.g. After 6 hours the pressuredropped and remained below 100 p.s.i.g. indicating the reaction wascomplete. Low boiling products were discharged overhead through a watercooled condenser into Dry Ice traps. Neohexene was obtained in 85 molepercent yield. The reactor residue contained collidine, neohexylchloride and collidine hydrochloride mixed with a small amount of thetar-like intermediate.

EXAMPLE 914 pounds of collidine and 455 pounds of neohexyl chloride (2:1mole ratio) were charged to a 200 gallon glass-lined stirred autoclave.Temperature was raised to 370 F. at which point neohexene was producedat a rapid rate and was discharged overhead through an efficient watercooled column at a rate sufficient to maintain a reactor pressure of 50p.s.i.g. The temperature of the reactor was raised to 410 F. as the rateof neohexene coming overhead decreased. The reaction yielded 268 pounds(85.5 mole percent) of neohexene. Plugging was encountered when anattempt was made to discharge the reactor residue through the 1 inchbottom draw of the autoclave. The plugging was caused by the solid phasewhich consisted of spheres, 2-5 millimeters in diameter, of collidinehydrochloride and the agglutinant intermediate EXAMPLE 6 1,030 pounds ofcollidine and 345 pounds of neohexyl chloride (3:1 mole ratio) wascharged to the 200 gallon autoclave. The operating procedure was thesame as that described in Example 5 with the exception that the finalreactor temperature was 444 F. The reaction yielded 212 pounds (89.5mole percent) of neohexene. The tarlike intermediate was absent and noplugging was encountered upon discharge of the reactor residue. Thecollidine hydrochloride was obtained as fine crystals slurried with theliquid phase remaining in the reactor.

EXAMPLE 7 795 pounds of collidine and 663 pounds of neohexyl chloride(1.221 mole ratio) were charged to the 200 gallon autoclave. Theoperating procedure was the same as that described in Example 5 with theexception that the final reactor temperature was 485 F. The reactionyielded 428 pounds (93 mole percent) of neohexene. The reactor residuewas the same as that described in Example 6. No plugging problem wasencountered.

EXAMPLE 8 Collidine and neohexyl chloride were fed continuously at a 3to 1 mole ratio to the 200 gallon autoclave at a temperature of 400 F.The pressure was changed to obtain the best possible purity of neohexenein the overhead without losing too much neohexene in the bottoms.Approximately 4 wt. percent neohexene was the least concentration in thebottoms at any pressure. The yield was low due to the slow reaction rateunder these conditions.

It is claimed:

1. A process for the production of substantially pure quaternary carbonatom-containing mono-olefins which comprises thermallydehydrohalogenating in the presence of collidine, a halogenatedhydrocarbon having the general formula:

wherein R is an alkyl radical of up to 8 carbon atoms, the total carbonatoms in the three R groups being up to 18; R is a divalent aliphatichydrocarbon radical of 2 to 8 carbon atoms; and X is a halogen having anatomic weight of 35 to 127, said collidine being present in at leastequimolar amounts based on the amount of halogenated hydrocarbon, at atemperature of about 300 to 370 F., for a time sufiicient to form anintermediate complex of collidine and said halogenated hydrocarbon anddecomposing the intermediate complex to provide said quaternary carbonatom-containing mono-olefin.

2. The process of claim 1 wherein the halogenated hydrocarbon is aneoalkyl chloride.

3. The process of claim 2 wherein the neoalkyl chloride is neohexylchloride.

4. The process of claim 1 wherein the decomposition is conducted at atemperature of at least about 440 F.

5. The process of claim 4 wherein about 1 to 20 moles of collidine arepresent, based on the amount of halogen- References Cited atedhydrocarbon.

6. The process of claim 5 wherein R is alkylene and UNITED STATESPATENTS X is substituted on a carbon atom which is beta to the 3,227,7701/1966 Burk et a1 260677 neo carbon atom 5 3,227,766 1/ 1966 Kruse et a1260 677 7. The process of claim 6 wherein the carbon atom beta to theneo-carbon atom is at the end of the carbon OTHER REFERENCES chain.Brewster & McEwe n, Organic Chemistry, third edi- 8. The process ofclaim 7 wherein about 1 to 5 moles tion, 1964, p. 740. of collidine arepresent, based on the amount of halogen- 10 ated hydrocarbor E. PrimaryEXLZHHIZEI.

9. The process of claim 3 wherein about 1 to 5 moles of L MYERS,Assistant Examinel. collidine are present, based on the amount ofhalogenated Ydrocarbon. US. Cl. X.R.

10. The process of claim 9 wherein the decomposition 15 260 683 15 isconducted at a temperature of about 440 F. to 500 F.

